Note:with a binary search (addition BINARY SEARCH is used for standard tables, automatically for sorted tables), if there are several hits (because of an incompletely specified search key or because there are duplicate entries in the table), then the first hit in terms of the sequence of the rows is always returned, that is, the row with the smallest index.
BINARY SEARCH in read table statement,布布扣,bubuko.com
BINARY SEARCH in read table statement
原文：http://www.cnblogs.com/ruingy/p/3594669.html